1. Field of the Invention
The present invention relates to new and useful improvements in two-stroke cycle gasoline engines and to new and useful improvements in exhaust valves for such engines. More particularly, the present invention provides a rotary exhaust valve which delays the opening of the exhaust port during the expansion stroke and, if desired, advances the closing of the exhaust port during the compression stroke while, at the same time, fully opening the exhaust port and permitting blow down and scavenging of the combustion chamber.
2. Description of the Prior Art
It has been know in the past to provide speed-controlled exhaust valves which will remain partially closed at slow speeds of the engine, delaying communication between the combustion chamber and exhaust passage beyond the usual opening of the exhaust port by the piston, and move upward, fully exposing the exhaust passage to the combustion chamber through the exhaust port, at high engine speeds. Such valves, however, do not provide the advantages of longer expansion and compression strokes while also permitting maximum scavenging.
In the parent application, United States Patent Application S.N. 096,551, now allowed, a novel exhaust control valve is disclosed employing a linkage to the crankshaft which providing opening and closing of the exhaust passage during each cycle of the engine. This invention provides many distinct advantages, including an improved power stroke, more efficient and thorough combustion of fuel, less short circuiting of combustible mixture, and improved performance of downstream pollution control devices, such as catalytic converters, due to higher and more uniform exhaust temperatures. Although the invention of the parent application is believed to function quite well, applicant has found that further improvements to the basic concept are possible through use of improved valve elements, which produce more effective valving, and improved drive mechanisms, which are simpler, lighter, and more reliable in operation.
Accordingly, it is a primary object of the present invention to provide an exhaust control valve which provides complete sealing of the exhaust passage when the valve is closed and provides minimal turbulent flow throughout its operation.
It is a further object of the present invention to provide a rotary exhaust control valve which directly utilizes the rotary movement of the crankshaft drive mechanism to control the actuation of the valve.
It is an additional object of the present invention to provide an exhaust control valve drive mechanism which provides a direct linkage between the crankshaft and the valve means.
It is another object of the present invention to provide an exhaust control valve which is relatively simple in design, provides reliable and straightforward operation and inherent ease of manufacture.